The sun is the primary source of energy for all natural processes on the earth and it has been an ultimate goal of technology to be able to create solar power systems that make use of all this free energy.
The problem has always been the efficiency at which the solar energy can be converted to something that can be used in the home and to provide power to industry. The main aim has been to convert the solar energy to electricity at a cost that compares well with current power systems.
The Drive to Solar Power Systems
A major drive towards solar power systems is the global initiative for cleaner power generation processes. Burning fossil fuels like oil, coal and gas not only uses up a limited resource but also pollutes the atmosphere with gases that can dramatically effect the environment.
Major initiatives are being driven by governments to use the sun to heat water such as the Southern Mediterranean Solartherm project. China is leading the way in the world in initiatives to ensure that it uses more renewable energy sources, especially including solar power. In a law passed in Feb 2005 , China is planning to have 10% of its energy provided by renewable sources by 2020.
ChinaDaily 2005-03-17 described the desired scenario: “Imagine this: You drive home late in the evening in a shiny new car powered by liquid fuel extract from the same rice crop you ate during dinner. Once home, you take a shower in water heated by the sun during the day. “
Solar Water Heating Systems
Many homes across the world are now having solar water heating systems installed as standard . These are usually not solar powered but instead have panels of tubing through which water is pumped that are placed in the direct sunlight to be heated.
This can be a cheap and low-tech method of capturing energy from the sun requiring only a small pump; a panel (similar to a central heating radiator) and a water tank. The restrictions with this type of system are that they work well only where there is plenty of sunshine and that they are only heating the water and not providing power for any other purpose.
Solar Powered Battery Chargers
Another, generally small scale, practical use of solar power is to charge battery cells. The efficiency of a solar panel is often not sufficient to drive a device directly but it can be an excellent source of power to keep a battery topped up especially for industrial devices such as out on the highway or otherwise remote from mains power supplies.
Solar powered battery chargers are particularly good for evening lighting or heating. The batteries can charge through the day, for perhaps up to 18 hours, to then provide light or heat for a few hours in the evening.
Solar Power System Components
Solar systems, whether they be for home or major industry are composed of the same basic components. The difference is mainly in scale of the parts although other factors such as methods of focusing the sun light, and also combining the system with a conventional power source, may be implemented.
The first major component is the solar panel. The solar energy needs to be converted to electricity and this is achieved with panels of a technology and size that reflect the power required and the budget available. Panels have a value of efficiency related to the power output per surface area.
Most solar panels have silicon photo-voltaic cells of which there can be hundreds contributing a small amount of the total power output. A new breakthrough has allowed development of a super thin photo-responsive alloy based on the discoveries of a South African team headed by Professor Vivian Alberts of the University of Johannesburg.
Panels are also categorized by their ability to survive in varying environments. Solar panels are selected depending on where they will be fitted as they may have to withstand extreme variations in temperature as well as monsoon rains and storm winds.
- Power System Batteries
As the suns power falling on any part of the earth’s surface varies greatly through the day, and from season to season, a critical part of any solar power system is the battery storage unit. The efficiency of the panels to convert solar energy to electricity is extremely important but it is just as important to reliably capture that energy to be able to release it when required.
The choice of battery unit will depend on the amount of power required and the output of the solar panels. The storage capacity can be calculated from the power requirement and length of time it will be required each day. The battery technology will depend on budget as well as service and safety specifications.
- System Control
Depending on the complexity of the solar power system, a level of control will be required to make the system as efficient as possible. The component may simply be a charging circuit to provide the right amount of charge current, or an intelligent system to turn solar panels to direct them to the sunlight. It may also control switching to an external power source when the solar system cannot provide sufficient power.
The Cost of Solar Power
Unlike most other sources of energy where the fuel, such as coal, oil or gas, must be extracted and pre-processed, the main cost of solar power systems is upfront for the equipment. Home systems would usually include large solar panels on the roof of the property, with connections to control systems and batteries. Larger industrial solar systems will have more complexity and expense to extract the highest level of efficiency.
Although the upfront cost is high, the majority of solar systems are low maintenance and need only occasional servicing. As with all systems, pumps and other moving parts need the most care. Depending on the type of batteries, they will usually need replacing at regular intervals to maintain their level of power storage.
Major Solar Power Plants
Individual home solar power systems can provide sufficient electricity for most home uses. There are also very large scale solar power plants such as the Planta Solar de Salamanca , in Spain, which produces up to 48 Mega Watt/Hours per year – enough to power 10,000 homes. This system uses millions of photo-voltaic cells.
Other large scale plants use reflectors to direct sunlight from a vast area onto oil filled pipes, fitted to the top of a high tower. The oil is heated and used to make steam, which is then used to generate electricity.
Government Grants for Solar Power
Many governments have a grant scheme designed to increase the amount of use of renewable energy. The US government has the Solar Energy Technologies Program which can greatly reduce the upfront cost of solar power systems.
 Union of Concerned Scientists – The Hidden Cost of Fossil Fuel
 European initiative – Solartherm – Solar Water Heating and Cooling in the Southern Mediterranean
 World Watch – Solar Energy Booming in China
 South Africa Web – Thin Solar Panels
 Florida State University – Solar Power Plant
 Kyocera Solar – Sole Supplier of Photovoltaic cells for Planta Solar
Resource: US Department of Energy – Solar Energy Resources